@@ -180,6 +180,16 @@ The interop calls three underscore-prefixed virtual-core members: `_willUpdate()
 
 This is a real coupling: a virtual-core release could change them without it being a documented breaking change. It is why the package pins an exact version rather than floating, and why every version bump re-verifies those three members before shipping.
 
+## Stopgaps for upstream fixes
+
+Behaviour that belongs in virtual-core, carried here only until the upstream fix ships:
+
+| Behaviour | Upstream | Stopgap |
+|---|---|---|
+| A `ScrollToIndex`, `ScrollToOffset`, `ScrollToEnd` or `ScrollBy` issued by code while a touch fling is still moving the list overshoots its target on Android: Chrome carries the fling on from the written position. virtual-core stops the fling first only on iOS 27. | https://github.com/TanStack/virtual/pull/1347 (issue https://github.com/TanStack/virtual/issues/1346) | `runScrollCommand` in `wwwroot/adaptive-virtualize-interop.js` hides the scroll axis's overflow for two frames before the write. Pinned by `ScrollToIndex_WhileATouchFlingIsMovingTheList_StopsTheMomentumBeforeWriting`. |
+
+⚠️ **Remove the stopgap together with the bump to the virtual-core release that contains the fix.** Until then it also runs on iOS, where it is not needed and costs its two frames, because telling the platforms apart would mean copying virtual-core's private user-agent checks.
+
 ## Vendored library provenance
 
 | | |
 
@@ -49,11 +49,6 @@ function compact(source) {
 
 const nextFrame = () => new Promise(resolve => requestAnimationFrame(() => resolve()));
 
-/** virtual-core's own iOS WebKit test, iPadOS desktop-class Safari included. */
-function isIOSWebKit() {
-	return /iP(hone|od|ad)/.test(navigator.userAgent) || (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 0);
-}
-
 class AdaptiveVirtualizeInstance {
 	// Keys and sizes arrive as two parallel arrays rather than one array of objects: this covers the
 	// WHOLE item set, not just the rendered window, and it crosses the interop boundary as JSON on
@@ -485,41 +480,54 @@ class AdaptiveVirtualizeInstance {
 	/**
 	 * Runs a scroll command, first stopping a touch fling that is still moving the list. Android
 	 * Chrome carries a fling on after a programmatic scroll write, so a jump issued mid-fling lands
-	 * wherever the momentum takes it instead of on its target. iOS WebKit stops the fling on the
-	 * write before iOS 27, and from 27 on virtual-core stops it itself, so iOS is left alone.
+	 * wherever the momentum takes it instead of on its target. virtual-core stops a fling before a
+	 * command only on iOS 27; this stands in for the rest until
+	 * https://github.com/TanStack/virtual/pull/1347 ships, and goes away with it.
 	 *
 	 * Hiding the scroll axis's overflow for two frames is what stops the momentum - the same trick
-	 * virtual-core uses on iOS 27. Its own _stopMomentum is not reused: it is private, and it drops
-	 * the callback of a command superseded mid-stop, which would leave that command's caller
-	 * awaiting forever. Without a touch there is no fling to stop, and on a desktop hiding the
-	 * overflow would also hide a classic scrollbar and reflow the list, so the write goes out at once.
+	 * virtual-core uses on iOS 27. It runs on iOS too, where it is not needed (before 27 the write
+	 * stops the fling itself, and on 27 virtual-core does) and costs those two frames: telling the
+	 * platforms apart would take copying virtual-core's private user-agent checks. Its own
+	 * _stopMomentum is not reused: it is private, and it drops the callback of a command superseded
+	 * mid-stop, which would leave that command's caller awaiting forever. Without a touch there is
+	 * no fling to stop, and on a desktop hiding the overflow would also hide a classic scrollbar and
+	 * reflow the list, so the write goes out at once.
 	 */
 	async runScrollCommand(command) {
 		const isTouchFling = this.lastInputWasTouch && !this.touchActive
-			&& this.virtualizer.isScrolling === true && !isIOSWebKit();
+			&& this.virtualizer.isScrolling === true;
 		if (isTouchFling) {
 			// Shared by every command issued during the same stop, so none of them reads back the
 			// "hidden" another one set as the value to restore.
-			this.momentumStop ??= this.stopMomentum().finally(() => { this.momentumStop = null; });
-			await this.momentumStop;
-			if (!this.cleanupMount) {
-				return;
+			this.momentumStop ??= this.stopMomentum()?.finally(() => { this.momentumStop = null; }) ?? null;
+			if (this.momentumStop) {
+				await this.momentumStop;
+				if (!this.cleanupMount) {
+					return;
+				}
 			}
 		}
 
 		command();
 	}
 
-	async stopMomentum() {
+	/** Hides the scroll axis's overflow for two frames; null when it had to be put back at once. */
+	stopMomentum() {
 		const element = this.isWindowScroller ? this.findScrollContainer(this.rootElement) : this.scrollContainer;
 		const property = this.options.horizontal ? 'overflow-x' : 'overflow-y';
 		const { style } = element;
 		const value = style.getPropertyValue(property);
 		const priority = style.getPropertyPriority(property);
+		const crossSize = () => this.options.horizontal ? element.clientHeight : element.clientWidth;
+		const crossSizeBefore = crossSize();
 		style.setProperty(property, 'hidden', 'important');
-		await nextFrame();
-		await nextFrame();
-		style.setProperty(property, value, priority);
+		// A classic scrollbar takes layout space, so hiding it would reflow the list for two frames
+		// (a touchscreen laptop). Put it back before anything paints and write at once, as before.
+		if (crossSize() !== crossSizeBefore) {
+			style.setProperty(property, value, priority);
+			return null;
+		}
+		return nextFrame().then(nextFrame).then(() => style.setProperty(property, value, priority));
 	}
 
 	cancelScroll() {
 
@@ -221,9 +221,16 @@ public async Task ScrollToIndex_WhileATouchFlingIsMovingTheList_StopsTheMomentum
         var runs = await _fixture.Page.EvaluateAsync<CommandSample[]>(
             "async () => {" + _mountScript + @"
                 const delay = ms => new Promise(resolve => setTimeout(resolve, ms));
-                const jumpWhileMoving = async byTouch => {
+                const jumpWhileMoving = async (byTouch, classicScrollbar) => {
                     const list = mount(200, {}, (totalSize, root) =>
                         setTimeout(() => { root.style.height = `${totalSize}px`; }, 30));
+                    if (classicScrollbar) {
+                        // A scrollbar that takes 15px of the width while it shows; the browser
+                        // under test hides its scrollbars.
+                        Object.defineProperty(list.viewport, 'clientWidth', {
+                            get: () => list.viewport.style.overflowY === 'hidden' ? 300 : 285,
+                        });
+                    }
                     await delay(100);
 
                     // The input that set the list moving: a touch that has already lifted - a fling -
@@ -254,7 +261,7 @@ public async Task ScrollToIndex_WhileATouchFlingIsMovingTheList_StopsTheMomentum
                     list.viewport.remove();
                     return sample;
                 };
-                return [await jumpWhileMoving(true), await jumpWhileMoving(false)];
+                return [await jumpWhileMoving(true, false), await jumpWhileMoving(false, false), await jumpWhileMoving(true, true)];
             }");
 
         // Assert
@@ -271,6 +278,13 @@ public async Task ScrollToIndex_WhileATouchFlingIsMovingTheList_StopsTheMomentum
         var wheel = runs[1];
         Assert.Equal("auto", wheel.OverflowWhenIssued);
         Assert.Equal(5000, wheel.ScrollTopWhenIssued);
+
+        // A scrollbar that takes layout space would vanish for two frames and reflow the list (a
+        // touchscreen laptop), so the overflow is put back before anything paints and the write
+        // goes out at once.
+        var classicScrollbar = runs[2];
+        Assert.Equal("auto", classicScrollbar.OverflowWhenIssued);
+        Assert.Equal(5000, classicScrollbar.ScrollTopWhenIssued);
         _fixture.AssertNoJsErrors();
     }